This definition clearly indicates that mind has something to do with body. It is experimentally proved that the body and mind are related. Mental functions and physical conditions interact with each other and hence they influence each other. There are many ways where the mind and body are influencing each other. This relationship is a two way process. That is, the functions of mind affects the body states and vice versa. Let us see some examples: effects of mind/mental functions on body, effects of body and physical processes on mind, genetics and behaviour, heredity, environment, brain and behaviour, neuron, synapse, nervous system and central nervous system, etc. Brain is the highest and the most important nerve centre. It is situated in the skull cavity. It comprises of the cerebrum, cerebellum, thalamus, hypothalamus, pons and medulla oblongata. In this background it may be described that,’ sensation is a process of shifting of information from sense organs to the brain’. The muscles are responsible for many types of movements and behaviours which are internal as well as external. The main characteristic of muscle tissue is its ability to contract and making movements possible. There are three types of muscles in our body. There are many glands in human beings situated in different parts of the body. They are of two types: (i) Duct glands and (ii) ductless or endocrine glands. Endocrine glands are more important from the point of view of behaviour. Endocrine glands release their secretions called ‘hormones’ directly into blood stream. The normal secretions of these hormones promote healthy and normal personality. But over or under secretion of these hormones affect the development of body, general metabolism, mental development and emotional behaviour. Some of the important glands which are directly related to the development of personality and behaviour are: pituitary gland, thyroid gland, parathyroid gland, adrenal glands and sex glands. In this way various glands in our body have control over our behaviour. The knowledge of these glands and their functions help nurses to understand various signs and symptoms of diseases and also the behavioural deviations associated with the activities of these glands. All these aspects clearly show that the nurses must try to understand the biological basis of behaviour, so that they can plan the appropriate nursing care for the patients.